Process of producing wrought iron



O y .1936- F. JOHANNSEN 2,047,562

PROCESS OF PRODUCING WROUGHT IRON Filed Nov. '7, 1955 reducingconditions Iron Ore lff (+reagenrs) g V, 0 g I i aimrsteam *Preheafing*Rducjionfoimn sponge Lumpmg "v gviummd WWI-QM oxidizing agents IiA iron+slags m vEN m R Friedrich Jahannsen- ATTORNEY Patented July 14, 1936UNITED STATES PATENT OFFICE raooass orrnonucmo wnouen'r mos ApplicationNovember 7, 1935, Serial No. 48,689

- In Germany August 25, 1934 3 Claims. (or. 75-32) July 3, 1934,hereinafter referred to as the "old process.

10 The objects of this invention and the advantages obtained by theproposed improvements will bebetter understood by critically reviewingthe old process and gathering the reasons why the old process wasunsatisfactory from economical points 15 of view.

The old process directly producing lumpe wrought iron is carried out inpractice preferably in a rotary metallurgical furnace o1 tubular designand essentially comprises the following steps:

:0 Causing a charge of ierriierous material, which is mixed withcarbonaceous reducing agents, for instance fuel in the form of groundcoke, to pass through the heated iurnace so as to be converted attemperatures ranging from 600-900 centigrades 25 into ironsponge-causing the charge to be further heated up to still highertemperatures, at which the iron sponge is about to lump, ranging iromabout 900 to 1400 centigrades,--causing a current of oxidizing gases toreact with the heated so charge, so as to oxidize i. e. burn a portionof iron oi the sponge and produce additional heat, sumcient for startingand accomplishing the lumping oi the iron of the sponge and forproducing from the iron oxides and the slag forming constituents 35, ofthe ore, which are fluxible by iron-oxide, slags rich in iron oxides andsufliciently liquid as to ilow out of the lumping iron,-causing ironoxides of said slags to be reconverted into lumped wrought, iron, by sode errnlning the quantity of fuel added 4o to the charg that asufilcient proportion 0! unconsed fuel is still present in the charge oning through the lumping zone and to the exit of the iumace, for reducingin one and the same cycle of reactions iron oxides of said sings,- andcausing said slags and lumped iron emded therein to flow from thefurnace.

Continued. practical experiments ate and other eiiorts directed tocarrying out the old process described under conditions of strictesteconomy, viz. with the object of economizing in the consumption of fuel.and reclaiming the greatest possible proportion oi iron from the-rawmaterial under treatment and in the shortestfpos- 55 slble time haverevealed, that certain procedures and features characteristic of the oldprocess were unsatisfactory.

a matter of fact by using for reaction with the heated iron sponge inthe lumping zone air, viz. a gaseous oxidizing agent, which is highly 5diluted with nitrogen, the efliciency oi. the process is curtailed,because incidentally introducing into the iurnaoe nitrogen togetherwith'the oxygen oi the air means heating up uselessly ballast matter, orwaste gases, which escape through the stack.

Another disadvantage connected therewith, which accrues from using air-agaseous medium diluted with. nitrogen-as oxidizing agent lies therein,that the progress of the lumping process proper is altogether relativelyslow, since the 0111-- 1 dizing reaction occurs only within a limitedarea and exclusively at thesuriace oi the charge,- and because theadditional heat, which must be generated is sometimes inadequate forproducing those thinly liquid slags desired and at such a,20 rate asrequired tor the timely lumping oi all the iron in the charge. v

The principal object of this invention is to overcome. the ai'oresaiddrawbacks inherent to the old lumping process concerned.

Other objects aimed at and advantages obtained will become incidentallyapparent hereinafter to experts in the metallurgical field. I

The nature and scope of this invention are briefly outlined intheappended c and will so be more fully understood from the followingspecification taken together with the accompanying drawing, in whichFig. 1 is a. cross section vertically tahen'through the lumping acne oia metallurgical furnace, which works according to this invention;

' Fig. 2 is a longitudinal section taken vertically through ametallurgical iurnace redesigned and fitted for the pee oi thisinvention with means for throwing thereinto .owrm solid to oxidizingagents for reaction with the heated. charge in the lumping zone As theresult or continued research work and practical experiments of edirected to materiallyj improving the old process with the objectsbriefly outlined alcove it has been i'ound, that for reaction with theheated iron sponge in the l ing zone oi the face-in addition to air ormate of airsolid oxidizing agents can be used to, advantage, namelyminerals and like sub= we. om'gen or oxygenic compounds, whic eitherdirectly give on oxygen, or which under the conditions prevailing in theigning zone produce carbon dioxide, which in I turn is decomposed intocarbon monoxide and oxygen.

Ferriferous ores of oxygenic nature and iron carbonates. including browniron ore (limonite),

red iron ore (hematite), spathic iron ore (sider ite) and magnetic ironore (magnetite) have proved to be suitable oxidizing agents, theirdecomposition and reactions with the heated sponge iron-hereinaftersymbolized Fe-assumably proceeding substantially according to thefollowing equations:

Magnetite Fe=oi+re=4reo Another list of minerals, which were tested andfound suitable for the purposes of this invention includes carbonates ofthe alkaline-earth metals including limestone CaCQa, magnesite MgCOa,dolomite CaMg(COa)z (calcium magnesium carbonatei, also carbonates andacid carbonates of the alkali metals, including NazCOa, K2002, NaHCOa,KHCOa; the oxidizing effect of those minerals depending assumably upondecomposi tions and reactions set forth in the following equations:

CaCOs=CaO+COa My observation and numerous tests made in the course oflumping processes carried out with the employment of different mineralslisted above as "oxidizing agents have proved, that the oxidation of theiron in the lumping zone of the furnace is not only materiallyintensified at the surface of the charge, but is also propagated andcarried forward by reason of the trundling motion of the g It hasfurther been found, that by the employ- I 7 ment of limestone, of alkalicarbonates and of alkali acid carbonates as oxidizing agents the sulfurcontent of the lumped iron is materially reduced as compared with theaverage sulfur content of the lumped iron produced by the old process,in which air alone is used as oxidizing agent. 5 I attribute thisphenomenon to the desulphurizing action of calcium and alkalies, whichis known in other metallurgical fields, and is supposed to be due toreactions proceeding according to the following equations:

A certain desulphurizing effect may be attributed to the presence ofwater or rather steam given off or produced by those minerals, used asoxidizing agents, in which water is either chemically bound in the formof water of crystallization, or which contain water as humidityassumably the said desulphurizing effect is accompanied by reactions anddecompositions occurring according to the following equations:

In Fig. 3 of the drawing a rotary metallurgical furnace F is shown byway of an example, which is fitted according to this invention withdispensing and feeding means adaptedto feed the solid oxidizing agentsconcerned in appropriate proportions and preferably in finely subdividedform into the lumping zone of the furnace.

Said dispensing and feeding means comprise: A bin B containing the solidreagents concerned, a rotary dispensing wheel W of known design enclosedin a shell and having a number of cells; means known per se and notshown,--whlch are under the control, of the operator and are providedfor controlling the revolving speed of said dispensing wheeI W withtheobject of adjusting according to temporary requirements the quantityof the solid oxidizing agents introduced into the furnace; a source ofcompressed air, supplied through pipe P, for blowing the oxidizingagents concerned, which slide down through duct D, into the furnace F.

Another pipe P2 is provided for feeding pulverulent, liquid or gaseousfuel into the furnace as required on starting the furnace to work or fortemporarily supplying additional heat-thus enabling the operator of theplant to cope with adverse circumstances, for instance, if the heatproduced in the furnace drops below the normal temperatures, at whichthe lumping of the iron 60 occurs.

- quantity of the solid oxidizing agents in finely subdivided form intothe furnace 13'.

Obviously the furnace F can be worked also exactly as previouslyproposed in my United States Patent No. 1,964,917,, namely with air"alone as oxidizing agent, by eliminating the dispensing device W andblowing or drawing a cor respondingly larger volume 'of air into thefurnace. 76

of operating metallurgical furnaces for the direct production of lumpedwrought iron, without sub- 'stantially deviating from the improvedprocess described hereinbefore, and without departing from the spirit ofthis invention.

For instance instead of compressed air steam may be used to advantage asgaseous medium for blowing the solid oxidizing agent; into thefurnace-particularly in cases, where the ferriferous raw material \mdertreatment or the solid oxidizing agents, or both, have a high sul phurcontent; steam seems to have also a de-' sulphurizing eii'ect upon thelumped iron, which I attribute to a chemical decomposition of the steamand the incidental production of hydrogen sulphide in the lumping zone.

Obviously the process modified and improved according to this invention,which is preferably carried out in a continuous manner, can be startedand carried out in one and the same furnace either with sponge iron orwith terriferous ores as the initial or basic raw material as indicatedin Fig. 3. 4

Instead of simply directing the above'described process to theproduction of lumped wrought iron from plain iron ores the improvedprocess may be 1 used in analogy to the teaching of'my United StatesPatent 2,026,683, for separating from iron ores and kindred materials,distinct by their content of iron-like companion metals, which howeverare reducible at higher temperatures than iron, viz. chromium,manganese, molybdenum, titanium, tunksten and vanadium-the saidcompanion metals.

In this case lumps of nought iron are obtained which are embeddedln'slags, the latter being relatively poor in iron but containingpractically all the bulk of the companion metal concerned, which is thenstill in unreduced condition and must be reclaimed therefrom bysubsequent treatment.

Likewise the process improved according to this invention may beconveniently directed in analogy to the teaching of my United Statespatent application Ser. No. 751,094, filed November, 1, 1934, to theproduction of lumped iron alloys, containing non-ferrous metals such asnickel, cobalt, which form alloys with the iron below the melting pointof the respective alloys, and which can be reduced in practice underabout the same conditions, particularly like temperatures, at which theiron is reduced.

In the latter .case lumps of ferro-nickel or another speciilc iron alloycontaining the respective nonferrous metal, are obtained embedded inslags, from which the said lumps are to be subsequently separated andare then ready for the production oh special alloyed steels.

comprises: causing a charge of sponge iron mixed with carbonaceous fuelto pass through a metallurglcal furnace, agitating the charge thereinand heating it up to temperatures. at which the ing agents to be'thro'wnupon the heated sponge iron for reaction therewith, whereby a proportionof the iron is bumtand additional heat is produced, sufllcient forstarting and accomplislflng the lumping of the iron and for producingfrom the iron oxides and the slag forming constituents of the charge,which are fluxlble by iron oxide, slags rich in iron oxides andsufllciently liquid as to flow out of the lumping iron, causing ironoxides from said slags to be re-converted into lumped wrought iron by sodetermining the quantity of fuel, added to the sponge iron, that asumcient proportion of unconsumed fuel is pres- -'ent in the charge onpassing through the lumping zone for reducing in one and'the same cycleof reactions iron oxides of said slags, and causing said slags andlumped iron embedded therein to flow from the furnace.

2. Process of producing wrought iron which comprises: causing a chargeof sponge iron mixed with carbonaceous fuel to pass through a metal-,lurgical furnace, agitating the charge therein and heating it up totemperatures, at which the sponge iron is about to lump,causing acurrent of oxidizing gases carrying with them solid oxidizing agents toimpinge upon the heated charge for reaction therewith, whereby aproportion of the iron is burnt and additional heat is produced,-

suflicient for starting and accomplishing the lumping of the iron andfor producing from the iron oxides and the slag forming constituents ofthe charge, which are fluxible by iron oxide, slags rich in iron oxidesand sufilciently liquid as to flow out of the lumping iron, causingiron'oxides from said slags to be re-converted into lumped wrought ironby so determining the quantity of iron is about to lump, causing a jetof steam carrying with it solid oxidizing agents to impinge upon theheated charge for reaction therewith, whereby a proportion of the ironis burnt and additional heat is produced, sufiicient for start- 1 ingand accomplishing the lumpingof the iron and for producing from the ironoxides and the slag forming constituents of the charge, which arefluxible by iron oxide, slags rich in iron oxides and suillcientlyliquid as to flow out of the lumping iron, causing iron oxides from saidslags to be re-converted into lumped wrought iron by so determining thequantity of fuel, added to the sponge iron, that a suflicient proportionof unconsumed fuel is present in the charge on passing through thelumping zone for reducing in one and the same cycle of reactions ironoxides of said slags, and causing said slags and lumpediron embeddedtherein to flow from the furnace.

FRIEDRICH JOH'AHNSEN."

